Data commit

Task/Percolation-Bond-percolation/Swift/percolation-bond-percolation.swift

@@ -0,0 +1,121 @@
+let randMax = 32767.0
+let filled = 1
+let rightWall = 2
+let bottomWall = 4
+
+final class Percolate {
+  let height: Int
+  let width: Int
+
+  private var grid: [Int]
+  private var end: Int
+
+  init(height: Int, width: Int) {
+    self.height = height
+    self.width = width
+    self.end = width
+    self.grid = [Int](repeating: 0, count: width * (height + 2))
+  }
+
+  private func fill(at p: Int) -> Bool {
+    guard grid[p] & filled == 0 else { return false }
+
+    grid[p] |= filled
+
+    guard p < end else { return true }
+
+    return (((grid[p + 0] & bottomWall) == 0) && fill(at: p + width)) ||
+            (((grid[p + 0] & rightWall) == 0) && fill(at: p + 1)) ||
+            (((grid[p - 1] & rightWall) == 0) && fill(at: p - 1)) ||
+            (((grid[p - width] & bottomWall) == 0) && fill(at: p - width))
+  }
+
+  func makeGrid(porosity p: Double) {
+    grid = [Int](repeating: 0, count: width * (height + 2))
+    end = width
+
+    let thresh = Int(randMax * p)
+
+    for i in 0..<width {
+      grid[i] = bottomWall | rightWall
+    }
+
+    for _ in 0..<height {
+      for _ in stride(from: width - 1, through: 1, by: -1) {
+        let r1 = Int.random(in: 0..<Int(randMax)+1)
+        let r2 = Int.random(in: 0..<Int(randMax)+1)
+
+        grid[end] = (r1 < thresh ? bottomWall : 0) | (r2 < thresh ? rightWall : 0)
+
+        end += 1
+      }
+
+      let r3 = Int.random(in: 0..<Int(randMax)+1)
+
+      grid[end] = rightWall | (r3 < thresh ? bottomWall : 0)
+
+      end += 1
+    }
+  }
+
+  @discardableResult
+  func percolate() -> Bool {
+    var i = 0
+
+    while i < width && !fill(at: width + i) {
+      i += 1
+    }
+
+    return i < width
+  }
+
+  func showGrid() {
+    for _ in 0..<width {
+      print("+--", terminator: "")
+    }
+
+    print("+")
+
+    for i in 0..<height {
+      print(i == height ? " " : "|", terminator: "")
+
+      for j in 0..<width {
+        print(grid[i * width + j + width] & filled != 0 ? "[]" : "  ", terminator: "")
+        print(grid[i * width + j + width] & rightWall != 0 ? "|" : " ", terminator: "")
+      }
+
+      print()
+
+      guard i != height else { return }
+
+      for j in 0..<width {
+        print(grid[i * width + j + width] & bottomWall != 0 ? "+--" : "+  ", terminator: "")
+      }
+
+      print("+")
+    }
+  }
+}
+
+let p = Percolate(height: 10, width: 10)
+
+p.makeGrid(porosity: 0.5)
+p.percolate()
+p.showGrid()
+
+print("Running \(p.height) x \(p.width) grid 10,000 times for each porosity")
+
+for factor in 1...10 {
+  var count = 0
+  let porosity = Double(factor) / 10.0
+
+  for _ in 0..<10_000 {
+    p.makeGrid(porosity: porosity)
+
+    if p.percolate() {
+      count += 1
+    }
+  }
+
+  print("p = \(porosity): \(Double(count) / 10_000.0)")
+}